This invention relates to the noninvasive measurement of body chemistry, and, more particularly, to the measurement of body chemistry using the response to light of externally accessible portions of the body.
The measurement of body chemistry is important in medicine, law enforcement, safety practice, and other fields. Body chemistry has traditionally been determined by obtaining fluid from the body, typically blood, urine, spinal fluid, and the like. A wet or spectral chemical analysis of the fluid is made and evaluated for the chemical content of the fluid.
In recent years, the effects of the use of illegal drugs such as narcotics and the excessive use of legal drugs such as alcohol have become important concerns for employers and others who may be affected by a person under the influence of such drugs. Drug testing programs, such as mandated testing for all prospective employees and random testing for persons in safety-sensitive positions, have become commonplace. Such testing is accomplished by obtaining fluid from the body and analyzing it as discussed previously. Apart from any question of legality of the testing, such testing is time consuming, expensive, invasive, and can cause physical discomfort or anxiety to some degree in those tested. The testing can also fail to achieve its desired objectives in some cases, as for example when a person has previously passed drug testing and thereafter uses an illegal drug shortly before performing a safety-sensitive function.
The majority of persons do not use drugs in an unacceptable manner. Invasive testing is, for those persons, a necessary burden both for those doing the testing and for the person tested. It would therefore be particularly desirable to have a reliable preliminary screening test to assess whether there was any reason to perform full quantitative testing in each case.
There is a need for an improved approach to determining body chemistry, such as the presence of drugs. Such an approach would desirably provide both a current state of body chemistry and information on the historical use of drugs, at least in a qualitative sen se. The approach would also desirably be noninvasive, painless, and fast so as to reduce any burden associated with the testing. The present invention fulfills this need, and further provides related advantages.